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Daniel

rear caliper handbrake mech

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I've just fitted new seals and noticed differences between now each caliper operates.

 

Firstly, I've fitted and rotated the piston so that it 'engages', and when I operate the arm/lever, the piston moves in and out (from completely pushed in). I assumed this would ratchet out?...... or does it work when the system is pressured up?

 

Secondly, if you look at the image below, you'll see that the left hand caliper has a small rubber ring under the arm.... in addition to this, the arm returns really slowly once pressed.
By contrast, the right hand caliper has no ring and operates smoothly and returns as quickly as your thumb allows it to.

I assume that even though the RHS caliper has no rubber ring, it operates correctly and that the LHS needs to be freed up?

 

2AF09061-5A21-45DC-9ECC-FB928D4946D0_zps

 

Cheers in advance you lovely people.

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Hi Daniel,

 

Don't think that ring should be there. Don't worry about the speed the arms move on their own, it's the big springs that pull them into position when hooked up.

 

The piston should ratchet out but not go back in if the splines are engaged to allow for pad wear. If the piston can be pushed back in then either the splines are not engaged or they are worn or the mechanism is busted. 

 

Pete

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Cheers Pete, that's what I thought.

 

The pistons appear new so I'm worried that the mechanism is broken.

 

I imagine if that's the case, it's new caliper time?

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That rubber ring is the seal around the shaft, and fits into a recess in the housing. The mechanism has moved out of the caliper...if you compare the two, it is obvious that the left hand one projects more than the right. If you operate the left hand one backwards and forwards and give it a good push in, then it should slowly move back to match the right hand one. A good squirt of WD40 or similar helps....it can take a while before it frees up. The seal having been displaced has allowed the shaft to corrode and get sticky. Then fit the return spring...and that holds the mechanism in the right place. Get some copper grease around the spindle, as there is a tendency for the whole thing to stick...and that prevents the return spring from resetting the operating arm. Then the self adjusting mechanism doesn't operate properly, as it needs the full range of movement for the internal ratchet to work correctly. If you undo the three cap head screws, then you can take the whole mechanism off....keep everything squeaky clean!!  Also make sure the cables operate freely...they can get all rusty and sticky and that stops the self adjusting, too.

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OK so a bit of WD40 and the RHS lever is now nice and free.... a bit of persuasion and I'm sure the rubber seal will seat too.

 

Seems odd though that the handbrake mech doesn't ratchet, the pistons actually appear new.

 

Do I need to pull them out slightly for them to engage?

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The handbrake mechanism on the pistons does not ratchet the pistons out.

 

The adjustment is advanced to the next click by normal braking action as the pads wear.

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Yeah, I was struggling to get the pistons to ratchet out though, which confirms that the mechanism is working. Anyway, they just need pulling out a tad and away we go.

 

They appear to be working beautifully now. Fingers crossed once they're back on the car!!

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Before you re-install, think about cutting a slot into the cable bracket to get the cable on/ off more easily in situ..

I did it for removal purposes, doubt the structural integrity is compromised as the bracket is substantial.

Will try to post pic tomorrow am.

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Oops, not the bracket at all, slots need to be cut into the caliper body of course:

image.jpg1_zpstlw2bo45.jpg

About to strip these down for rebuild and repaint, but still undecided on the colour.

Body is helleblau A15 ( light metallic blue, a bit richer than ice blue) if anyone has any suggestions..

Thx

Dave

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Interesting. When I rebuilt my calipers and tested the mechanism, they ratcheted out.

 

Also worth making the hole in the lever where the end of the cable wire fits in. That's an annoying job when refitting.

 

Go silver or gold on the calipers!

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Thanks Peter,

Having just done the fronts, and found out how little corrosion it takes to impair correct operation, I'll defo strip the rears too.

just testing mine also has the piston move out under hand pressure on full range of handbrake lever movement. Will now check to make sure they can't be pushed back.

Silver or gold? I like gold! Suggestions for the best type of paint anyone?

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My refurbished rears were finished in gold. They came from Lotusbits. I painted the fronts silver with POR15 when I refurbed them which I think looks quite good through the silver wheels. Discreet. With the rears being inboard you don't really see them except from underneath so colour's not really a factor.

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I rebuilt mine a while ago and now the drivers side hand brake is sticking again! I know the hand brake cables also could do with replacing, but I am interested in changing the calipers for some thing newer any one done an upgrade with other calipers?

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Rob, I had my callipers rebuilt, but my handbrake occasionally came on (drivers side) whilst I was driving - bit disconcerting that was.

 

Once the cable was replaced, all has been fine, hand brake holds the car no problem.

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This is great answers most questions I had for you guys this morning.  One final question:

I know some cars have rotating pistons.  I assume due the age of these cars that these do not.  They just move in and out?

 

Thanks

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Yes just in and out - fixed by locating with a 'hump' in the back of the pad (for pad replacement, need to be rotated through 45 degrees to allow piston to be pushed back into caliper 

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OK Thanks

 

No piston movement at all when I move the handbrake cable lever.  Handbrake was not great either before it came of the road so think a strip down is required.

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Phil, mine were stuck to buggery in the caliper bodies.

Dad actually used a modern piston gun to screw them back in ( against my advice, but it did work). Pics of the mech:

image.jpg12_zpsbwmd9cqt.jpg

image.jpg14_zpsjkqh4xnf.jpg

Didnt take much crud on the piston to sieve it completely.

I assume the screwing it back approach worked because the piston was able to slip back a little every time the splines hit the 45 degree mark. Mine are back together now and working properly on the bench, but I'd try the lining up and popping them out method first, just in case

It took 100psi to pop the Pistons out in the end, including soaking them in WD for a while

Hope the above pics help.

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Dave

 

Thanks for this but dont quite understand.  The part that moves when the handbrake lever is pulled is free and extends around 3 mm.  Is this about right.  Returns freely when lever is released.

I dont quite understand the 45 degree bit. I am assuming my piston will not just push out.  I have to turn? and then push out?

post-13610-0-07651000-1436710616.jpg

Edited by PhilW

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If I'm seeing your pic correctly, you have the back off the caliper already?

Didn't do this on mine yet, but do I assume you can see the threaded pin on the back of the piston now that the back plate is off? If so, then I think you've already separated the piston pin from its ratchet mechanism.

Yes, 3 mm sounds about right for movement, the ratchet effect takes up the pad wear when the piston's teeth are engaged with the mechanism.

The 45 degree bit is for removing the piston from the assembled caliper ( turn so that the slots in the pad face of the piston are at 45)

Hope this isn't confusing...

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Dave

 

Have had a look tonight. I only looked at one caliper and am able to push the piston in and out with a G clamp quite easily.  For the 45 degree bit do you mean turn as per the picture and then it will push out?

post-13610-0-67069500-1437075711.jpg

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Exactly right,

for assembled caliper.... It looks to me that the back plate you have removed (post#20) is the retaining /ratchet mechanism in the first pic in my post #19.

Hence, with the backplate off, the piston should be free to move without the alignment.

Once you have the backplate on, however, the 45 degree angle is essential to allow the piston to be fully depressed into the caliper

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